７５ Aging in Space

○In the universe aging progresses ten times. [1]
：decreased muscle strength, bone density, circulatory function and immunity, abnormal lipid and sugar metabolism
・After a certain age, people on Earth start to lose mass in their bones, typically at a rate of about 1-to-2 percent a year. But in space, those people lose bone mass at a greatly accelerated rate: as much as 1-to-2 percent a month.
Image credit: NASA

○Cause of aging: weightlessness and otolith
・In the zero gravity state, abnormality occurs in the otolith (connected with autonomic nerves and muscles of the whole body).
・Luckily, skeletal systems of the astronauts usually return to normal once they've spent some time back on terra firma.[1]
※Otolith [2]